(a) Field of the Invention
The present invention relates to a chuck structure adapted for use with an electrically or pneumatically operated drill having a power shaft, more particularly to a chuck structure adapted to be hand-tightened and having locking and positioning functions.
(b) Description of the Prior Art
A conventional drill bit clamping structure mainly includes a rotary shaft connected provided with a chuck body. The body is externally provided with a rotatable adjustment shell and a fixed shell. The body is internally and annularly provided with a plurality of slanting clamp pawls. The user may rotate the adjustment shell to match the turning of the threads to control the clamp pawls to obliquely advance or withdraw to thereby achieve the object of bit clamping or release.
However, in the above-mentioned structure, after locking, the adjustment shell is in a non-positioning state, which may lead to loosening of the clamp pawl and hence falling of the bit, so that the user may have to stop operation and re-lock the bit. This is not only inconvenient to the user, it may also cause danger to the user.